Background: It is not known whether the improved folate status from mandatory folic acid fortification had any impact on indexes and prevalence of anemias in the United States.
Objective: We investigated trends in indexes and prevalence of anemia and macrocytosis with a focus on comparison of prefortification data with postfortification data.
Design: Hemoglobin, hematocrit, mean corpuscular volume (MCV) and prevalences and likelihood of anemia and macrocytosis were determined for 26,596 adults examined in the National Health and Nutrition Examination Surveys, 1988-2004.
Results: From 1988-1994 to 1999-2004, hemoglobin modestly but significantly improved from 15.1 to 15.4 g/dL (approximately 2.0%; P < 0.0001) and from 13.3 to 13.6 g/dL (approximately 2.3%; P < 0.0001) in men and women, respectively. There was a significant increase in MCV from 1988-1994 to 1999-2004 in men (from 90.2 to 90.7; P = 0.0123) and older (>60 y) men (from 91.6 to 92.4; P = 0.0105) and in women (from 90.7 to 91.4; P = 0.0141). Only in women was the prevalence of anemia significantly lower in 1999-2004 than in 1988-1994 (27.9% reduction; P = 0.0005). The odds of having anemia in the postfortification period relative to the prefortification period was 0.64 (95% CI: 0.54, 0.75; P < 0.0001) in women and 0.79 (95% CI: 0.62, 0.99; P < 0.0433) in men. In general, the prevalence of macrocytosis and the odds of having macrocytosis did not change significantly from 1988-1994 to 1999-2004.
Conclusion: The improvement in hemoglobin and the decreased prevalence of anemia from 1988-1994 to 1999-2004, especially in women, may be attributable to improved folate status, increased vitamin/mineral supplements use, and other unknown causes after the initiation of folic acid fortification. The cause of increased MCV in men, and in older persons of both sexes, warrants further investigation.